1. Field of the Invention
The present invention relates to a knocking sensor that is attached to an engine block or the like of an internal combustion engine and used to detect knocking in the internal combustion engine, and in particular, to a knocking sensor which includes a piezoelectric element, a support member supporting the piezoelectric element, and a resin coating covering the piezoelectric element and at least part of the support member.
2. Description of the Related Art
A knocking sensor is known which is attached to an engine block or the like of an internal combustion engine and used to detect knocking in the internal combustion engine. For example, Patent Documents 1 and 2 describe such a knocking sensor.
A knock sensor (knocking sensor) of Patent Document 1 includes a support member which has a cylindrical pressure sleeve (insertion portion) and a flange-shaped collar portion (support body portion) provided at the base end of the pressure sleeve (see FIG. 1 and related description of Patent Document 1). On an outer circumference of the pressure sleeve, a piezo-ceramic plate (piezoelectric element) or a contact plate, an insulating plate, a mass, and the like are disposed and supported by the collar portion. The piezo-ceramic plate and the like are covered and sealed by a plastic case (resin coating) which is formed by molding.
With this knock sensor, in order to improve the sealing property of the support member and the plastic case, two grooves are provided on the outer circumference of the support member on the leading end side of the pressure sleeve. Two grooves are also provided on the outer circumference of the collar portion.
A knock sensor (knocking sensor) of Patent Document 2 includes a cylindrical core metal (support member) which has a cylinder portion (insertion portion) and a collar portion (support body portion) provided at the base end of the cylinder portion (see FIG. 1 and related description of Patent Document 2). On the outer circumference of the cylinder portion, a piezoelectric element or an electrode plate, an insulating plate, a weight, and the like are disposed and supported by the collar portion. The piezoelectric element and the like are covered and sealed by a resin coating which is formed by molding.
With this knock sensor, in order to improve the sealing property of the cylindrical core metal and the resin coating, two grooves are provided on the outer circumference of the cylindrical core metal on the leading end side of the cylinder portion. Two grooves are also provided on the outer circumference of the collar portion. With this knock sensor, each groove is formed such that the width thereof in the axial direction becomes smaller toward the diameter direction outer side. Consequently, it is unlikely that resin inserted into each groove will fall off or that the resin coating will become separated.
Patent Document 1 JP-T-2003-517593 (the term “JP-T” as used herein means a published Japanese translation of a PCT patent application)
Patent Document 2 JP-A-2004-257834
3. Problems to be Solved by the Invention
However, with the knock sensor of Patent Document 1 and the knock sensor of Patent Document 2 with an improved sealing property of the cylindrical core metal and the resin coating, it is difficult to ensure sufficient seal durability. Further, the knock sensor of Patent Document 2 has a problem in that it is difficult to form the groove.
The invention has been made in consideration of the above, and an object of the invention to provide a knocking sensor having improved seal durability for a support member and a resin coating.
According to a first aspect, the present invention provides a knocking sensor comprising: a piezoelectric element; a support member having a support body portion, the support body portion including a support surface directly or indirectly supporting the piezoelectric element; and a resin coating covering the piezoelectric element and at least part of the support member, the resin coating having an outside portion covering an outer circumference of the piezoelectric element and an outer circumference of the support body, wherein in an orthogonal direction orthogonal to the support surface, the side which the support surface faces is designated a leading end side and the opposite side is designated a base end side, and in an interfacial direction along the support surface, the side facing the outer sides of the piezoelectric element and the support body portion is designated an interfacial direction outer side, and the side facing the inner sides of the piezoelectric element and the support body portion is designated an interfacial direction inner side, the support body portion of the support member has a first engagement portion on the base end side thereof, the resin coating has a curved portion which extends from the outside portion toward the interfacial direction inner side and which curves toward the base end side of the support body portion, the curved portion including a second engagement portion which engages the first engagement portion.
Further, according to a second aspect, the present invention provides a knocking sensor comprising: an annular piezoelectric element; a support member having a support body portion which includes a support surface directly or indirectly supporting the piezoelectric element, and an insertion portion which extends from the support body portion and is inserted into the piezoelectric element; a resin coating covering the piezoelectric element and at least a part of the support member, wherein in an orthogonal direction orthogonal to the support surface, the side which the support surface faces is designated a leading end side and the opposite side is designated a base end side, and in an interfacial direction along the support surface, the side facing the outer sides of the piezoelectric element and the support body portion is designated an interfacial direction outer side, and the side facing the inner sides of the piezoelectric element and the support body portion is designated an interfacial direction inner side, the resin coating has an outside portion which covers an outer circumference of the piezoelectric element and an outer circumference of the support body portion, and a leading end-side portion which extends from the leading end side of the outside portion and which covers the leading end side of an outer circumference of the insertion portion, and the support member and the resin coating have at least one of a combination of a first engagement portion which is provided on the base end side of the support body portion, and a base end-side curved portion which extends from the outside portion toward the interfacial direction inner side and curves toward the base end side of the support body portion, the base end-side curved portion including a second engagement portion which engages the first engagement portion, and a combination of a third engagement portion which is provided on the leading end side of the insertion portion, and a leading end-side curved portion which is included in the leading end-side portion, extends toward the interfacial direction inner side, and curves toward the leading end side of the insertion portion, the leading end-side curved portion including a fourth engagement portion which engages the third engagement portion.